Method of reducing oxalic acid and its derivatives by electrolysis.



PATBNTED SEPT. 5, 1905.

4 E. VDN POR'IHEIM. METHOD 0F RBDUCING OXALIC ACID AND ITS DBRIVATIVES BY BLBGTROLYSIS.

APPLICATION FILED JAN. 29, 1904.

\\\ YYY\ vUNITED STATES PATENT OFFICE.

EMIL VON PORTHEIM, OE PRAGUE, AUSTRIA-HUNGARY.

METHOD OF REDUCING OXALIC ACID AND ITS DERIVATIVES BY ELECTROLYSIS.

Specification of Letters Patent.

Patented Sept. 5, 1905.

Application filed January 29,1904. Serial No 191,192.

Be it known that I, EMIL voN PoR'rHuIM, a subject of the Emperor of Austria-Hungary, residing' at Prague, Bohemia, Austria-Hungary, have invented certain new and useful Improvements in Methods for Reducing Oxalic Acid and its Derivatives b v Electrolysis, of which the following is a specification.

Oxalic acid has hitherto been reduced by the electrolytic process to glycolic acid. This is all that has been known so far about this matter. I have found that by moderating the process of reduction glyoxalie acid is directly obtained, for the preparation of which acid no practical method has been hitherto known. Furthermore?, l have reduced the esters and the amids of the oXalic acid with very satisfactory results, respectively, to esters and amids of the glyoxalic acid, said reduction being unknown till now. On the other hand, .l have reduced by the same method the oxanilic acid and its derivatives to phen ylglycin, CsHNOg.) The rational formula is Calif.. -N H. -Gl-Ig. -COH (or phenylglycocin) and its derivatives. 1nvariably in all of the foregoing processes when treating the mono and di substitutional derivatives of the oxalic acid one carboxyl group only is reduced, while the other is preserved.

The drawing accompanying this specification illustrates in sectional elevation one form of an apparatus by which the method can be carried out, and in the drawing A denotes a receptacle containing' two electrodes a. respectively, and said receptacle is divided by a diaphragm c.

In carrying out the said process I employ electrodes made of lead or of mercury, &c., said electrodes being separated by a diaphragm or by other suitable means, and for the bath diluted sulfuric acid is employed. The materials to be reduced are dissolved in the dilutcd sulfuric acid in the cathode-compartment and are then electrolyzed in employing a current possessing the intensity of about three amperes to one square decimeter at 15O centigrade. However, the degree of concentration of the sulfuric acid, the temperature, and the density of the current have to be altered according to requirements in each particular case.

First mamaria-At the cathode oXalic acid is dissolved in diluted sulfuric acid of two and one-half per cent. concentration. The electrolysis is then started, and by titration with a solution of phenylhydrazine the increment of glyoxalic acid is ascertained. Then the. maximum is reached or just overpassed, the electrolysis is interrupted. The solution of glyoxalic acid is freed from the remaining small quantities of sulfuric acid by barium hydrate and retains no impurities, with the exception of a slight trace of glycolic acid.

Second@ramp/a. The dimethylester of oxalic acid is dissolved in the cathode liquid and electrolyzed. The methyl ester of glyoxalic acid is obtained in a very satisfactory yield. This ester has been identiiied by the reaction of transforming it into its phenylhydrazon, the description of which has been given by Harries, (we [ferie/1jr' 1/1' hariw/wn Ulu/misc/cn Gasse/[.vc/mff, 36, 1936.)

Tz/NZ amv/1y)@.MOXalylanthranilic acid is dissolved in sulfuric acid of about eighty per cent. concentration and reduced by electrolysis. The formation of phenylglycin (o) carboxylic acid can be quantitatively ascertained by nitrite. The yield is a very satisfactory one. Finally, the sulfate of the phenylglycin carboxylic acid is freed from the excess of sulfuricacid by crystallization.

1t may be mentioned that according to the lapsed German patent to Kopp t Co., No. 64,909, dated January 19, 1892, oxanilic acid, its esters, and amids are said to be reduced to glycins by treating them with zinc alone or with zinc and acids or sodium amalgam. In fact, only traces of glycins are obtained by employing this method, so that my method is the very first to obtain glycins out of oxalic acid.

I claim A method of obtaining glyoxalic acid, its esters and amids from compounds containing the radical oxalyl (C202) Consisting in dissolving the compound to be treated in dilute sulfuric acid iu the cathode-compartment of an electrolytic apparatus, and then electrolyzing said solution at a low or moderate temperature.

In testimony whereof I have hereunto set my hand in presence of two subscribing witnesses.

EMIL VON PORTI-IERI.

lVitnesses:

ADoLPH FISCHER, ARTHUR Soi iwuz.

IOO 

